A transformer-coupled resonant converter can be generally defined as a converter in which a DC or rectified AC source is switched at a controllable frequency across the series and/or parallel combination of two or more reactive elements (a tank circuit) and in which the tank current is coupled to a load circuit through an isolation transformer. The simplest of resonant converter topologies is a two-element series converter in which the tank circuit comprises the series combination of a capacitor and an inductor. Additionally, a second inductor may be advantageously connected in parallel with the primary winding of the isolation transformer to provide boost capability--that is, allowing the converter to produce an output voltage higher than its input voltage.
Physical mechanization and packaging of the above-described converter circuits present a significant challenge, particularly when cost and package size are to be minimized. In a converter incorporating the above-described elements, for example, the circuit layout must accommodate an isolation transformer and two additional inductors. Clearly, a design the minimizes package size and cost is desired.